Frequency-Hopping PWM for Light-Load Efficient Switching Regulators
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Solution Overview
Problem
Conventional pulse-width modulation (PWM) in switching regulators results in reduced light-load efficiency due to high switching losses, while pulse-frequency modulation (PFM) provides better efficiency but leads to an unpredictable spectrum, making it unsuitable for spectrum-sensitive circuits.
Innovation Solution
A modulator that generates a pulse-width-modulated signal with a frequency automatically chosen from pre-defined frequencies, all being integer multiples of a fundamental frequency, allowing for smaller inductive and capacitive elements and improved power efficiency at light loads while maintaining a predictable spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional PWM is used at MHz-range frequency, then the switching regulator can use smaller inductive and capacitive elements, but the light-load efficiency is significantly degraded due to high switching losses
Solution Approach 1:
The modulator dynamically adjusts the PWM frequency based on the load current level. When the load current is high, the frequency is increased to MHz-range to enable smaller inductive and capacitive elements. When the load current is reduced, the frequency is automatically lowered to reduce switching losses and improve light-load efficiency. This dynamic frequency adjustment resolves the contradiction between component size and energy loss.
Solution Approach 2:
The invention changes the operating parameter (frequency) of the PWM modulator based on load conditions. By varying the frequency parameter from MHz-range at full load to lower frequencies at light load, the system optimizes both component size and efficiency across different operating points, resolving the contradiction between these two parameters.
2Loss of energy
If PFM is used to reduce switching loss and improve light-load efficiency, then the spectrum of the output voltage becomes unpredictable at different load levels
Solution Approach 1:
The modulator dynamically selects from multiple pre-defined frequency values that are all integer multiples of a fundamental frequency. This dynamic adjustment maintains predictable spectral components at multiples of the fundamental frequency while adapting to different load conditions, resolving the contradiction between efficiency and spectrum predictability.
Solution Approach 2:
The invention changes the frequency parameter within a constrained set of discrete values (integer multiples of fundamental frequency). This controlled parameter change allows efficiency optimization while maintaining spectral predictability, as all possible frequencies share common harmonic relationships with the fundamental frequency.
3Stability of the object's composition
If PWM is used at fixed frequency to maintain predictable spectrum, then the switching loss increases and light-load efficiency decreases
Solution Approach 1:
The modulator transitions from fixed frequency to dynamic frequency selection, where the frequency is automatically adjusted based on load current. This dynamic behavior reduces switching losses at light load while maintaining spectrum predictability through the constraint that all frequencies are integer multiples of a fundamental frequency.
Solution Approach 2:
The frequency range is segmented into multiple pre-defined discrete values rather than being fixed. This segmentation allows the system to select appropriate frequency levels for different load conditions, optimizing efficiency while maintaining spectral structure through the integer multiple relationship with the fundamental frequency.
Data Source
AI summary
A frequency-hopping pulse-width modulator is disclosed, which facilitates a switching regulator to use smaller-size inductive and capacitive elements, to have an improved power efficiency at light load, as well as predictable spectrum at different load levels. The improved modulator automatically determines the switching frequency of a switching regulator according to the load current delivered by the switching regulator from a number of pre-defined frequencies, which are all multiples of a fundamental frequency. By designing the maximum switching frequency of frequency-hopping pulse-width modulator in the MHz range, a switching regulator is able to use smaller-size inductive and capacitive elements. Light-load efficiency of the switching regulator with the frequency-hopping pulse-width modulator is also greatly improved as switching frequency of such switching regulator is reduced with decreased load current. More importantly, spectrum of a switching regulator with the frequency-hopping pulse-width modulator is as predictable as spectrum of a switching regulator with a conventional pulse-width modulator operated at the fundamental frequency.